Chain tensioner

ABSTRACT

A tensioning device for traction device, particularly chains, comprises an element, particularly a tension shoe ( 1 ) that tensions the traction device. The tension shoe ( 1 ) is mounted on a pivot axle ( 2 ) for pivoting relative to a base element ( 3 ), and a spring element ( 4 ) acting between the tension shoe ( 1 ) and the base element ( 3 ) urges the tension shoe ( 1 ) against the traction device. To simplify the assembly of the tension shoe ( 1 ) and the base element ( 3 ), it is proposed that one of the elements ( 1, 3 ) comprises at least one mounting eye ( 6, 11 ) having a radial mounting aperture ( 7, 12 ) for radially receiving the pivot axle ( 2 ) arranged on the respective other element ( 1, 3 ).

FIELD OF THE INVENTION

The present invention concerns a tensioning device for traction means,particularly chains. Such chain tensioners are used, for example, fortensioning the timing chain and for tensioning the chain of auxiliaryunits of diesel and Otto engines.

BACKGROUND OF THE INVENTION

A chain tensioner of the pre-cited type is known, for example, from DE-A195 36 643. A tension shoe is mounted on a pivot axle for pivotingrelative to a base element. A spring means is arranged between thetension shoe and the base element to urge the tension shoe against thechain. The tension shoe comprises a closed mounting eye into which thepivot axle fixed to the base element is axially inserted. A perfectcentering of the mounting eye with the pivot axle is required for theassembly of the base element and the tension shoe. Centering is achievedby a relative displacement of the base element and the tension shoe.After the centering operation, the pivot axle can be inserted into themounting eye by an axial displacement of the base element and thetension shoe relative to each other. Thus, for assembling theseelements, it is necessary to operate in different planes, and this isparticularly disadvantageous in automated mounting.

SUMMARY OF THE INVENTION

It is therefore the object of the present invention to simplify theassembly of the two elements. The invention achieves this object by thefact that one of the elements comprises at least one mounting eye havinga radial mounting aperture for radially receiving the pivot axlearranged on the respective other element. In the tensioning deviceaccording to the invention, the assembly of the two elements is effectedin one plane or in parallel planes. The base element and the tensionshoe must be aligned to each other only in such a way that as a resultof relative radial displacement between the elements, the pivot axleengages into the radial mounting aperture and thus into the mountingeye. If the radial mounting aperture has a flared mouth, theintroduction of the pivot axle is further simplified. In particular,radial displacements in a plane perpendicular to the one plane are notrequired. It is understood that the invention also applies to tensioningdevices in which a tension roller is used in place of a tension shoe andis mounted for rotation on a lever which comprises the mounting eyeaccording to the invention for receiving the pivot axle.

In other words, the tensioning device of the invention for a tractionmeans is comprised of a tensioning shoe (1), that tensions the tractionmeans, and comprising a further base element (3), on which thetensioning element (1) is mounted for pivoting on a pivot axle (2), aspring means (4) arranged between the elements (1, 3) urging thetensioning element (1) against the traction means, wherein one of thetwo elements (1, 3) comprises two horseshoe-shaped spaced-apart forkarms (5, 10) each of which comprises a mounting eye (6, 11) having aradial mounting aperture (7, 12) for radially receiving the pivot axle(2), and the other of the elements (1, 3) comprises a radial projection(1, 3) which engages between the forks (5, 10) and is overlapped by theforks (5, 10) on both the elements (1, 3) for snap engagement without aseparate fastener, there are corresponding arranged retention surfaces(8, 9) which extend coaxially with the pivot axle (2) and which, withinan operation-dependent pivoting range of the tensioning device, aresituated opposite each other and face each other, a radial displacementof the pivot axle (2) out of the radial mounting aperture (7, 12) beingprevented by a contact of the retention surfaces (8, 9) with each other.

Further embodiments of the invention offer other special advantages overprior art solutions. If one of the two elements comprises twospaced-apart fork arms and each of these fork arms comprises a mountingeye having the radial mounting aperture, the respective other elementcomprises a radial projection which is arranged between these fork armsand overlapped by both fork arms. Thus, after the assembly of the twoelements, an axial slipping-apart of these elements is reliablyprevented. In the prior art chain tensioner, it is necessary in somecases to use additional securing elements, for example a locking ring,which can be mounted only after the assembly of the two elements.

The pivot axle may be fixed, for example, on the base element and haveends projecting from both sides of the base element. Each of these endsthen engages into one of the radial mounting apertures of one of thefork arms which are fixed on the tension shoe. The pivot axle may bemade, for example, in one piece with the base element out of plastic. Anequivalent solution consists in that the pivot axle is fixed on thetension shoe and has ends projecting from both sides of the tensionshoe. Each of these ends then engages into one of the radial mountingapertures of one of the fork arms which are fixed on the base element.The tension shoe and the pivot axle can be made without any problem inone piece, for example, out of plastic.

Making the pivot axle in one piece with one of the two elements offersfurther advantages over prior art solutions. In prior art solutions, aseparate pivot axle made of a metal is pressed into the base element.This necessitates the machining of a reception bore in the base element.Besides this, means have to be provided for securing the pin fromfalling out of the reception bore. This can happen if the pin and thebase element are made of different materials having different thermalexpansion properties and the tensioning device is subjected to hightemperatures. All of these measures can be avoided if the pivot axle andthe element concerned, i.e. the base element or the tension element, aremade in one piece with each other. It goes without saying that theseadvantages are also obtained if, as in the prior art, the mounting eyefor receiving the pivot axle has a closed configuration in peripheraldirection.

To prevent the pivot axle from being displaced radially out of themounting eye, it is proposed to arrange on both the elements, retentionsurfaces which extend coaxially with the pivot axle and which, within anoperation-dependent pivoting range of the tensioning device, aresituated opposite each other and face each other. A radial displacementof the pivot axle out of the radial mounting aperture is prevented by acontact of the retention surfaces with each other. The retentionsurfaces can be made by providing a convex retention surface on thetension shoe and a concave retention surface on the base element.Outside of the operation-dependent pivoting range of the tensioningdevice, the tension shoe can take a position of pivot relative to thebase element in which the convex retention surface is disengaged fromthe concave retention surface. In this position of pivot, the pivot axlecan be removed without any problem in radial direction out of themounting eye. It is also possible to assemble the tension shoe and thebase element in the said position of pivot. When the pivot axle has comeinto its pre-defined position in the mounting eye, the tension shoe canbe pivoted about its pivot axle till the retention surfaces come to besituated opposite each other. In this arrangement, the pivot axle isretained perfectly in the mounting eye.

In the position of pivot intended for the assembly of the base elementand the tension shoe, an additional securing device may become necessaryfor preventing the pivot axle from slipping radially out of the mountingeye. This is the case, for example, when the chain tensioner,pre-assembled in the above manner, has to be transported. It isadequate, in this case, to provide a constriction on the radial mountingaperture with a clear width smaller than the diameter of the pivot axle.In this embodiment of the invention, the pivot axle snaps into themounting eye and a radial slipping out of the mounting eye is onlypossible by application of a higher force.

The embodiments of the invention described herein create tensioningdevices for traction means which do not require additional securingmeans after the assembly of the base element and the tension shoe; thepivot axle is reliably retained in the mounting eye in a simple manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a chain tensioner according to the invention,

FIG. 2 is a top view of the chain tensioner according to the inventionshown in FIG. 1,

FIG. 3 is a view of a further chain tensioner according to theinvention,

FIG. 4 is a partial top view of the chain tensioner shown in FIG. 3, and

FIG. 5 shows the assembly of the chain tensioner according to theinvention shown in FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

In the chain tensioner according to the invention represented in FIG. 1,a tension shoe 1 is mounted on a pivot axle 2 for pivoting relative to abase element 3. Between the tension shoe 1 and the base element 3 isarranged a spring element 4 which is supported at one end on the baseelement 3 and, at the other end, urges the tension shoe 1 against achain, not represented.

As can be clearly seen in FIG. 2, the pivot axle 2 is made in one piecewith the base element 3. The pivot axle 2 projects from the base element3 on both sides. The tension shoe 1 comprises two spaced-apart fork arms5 each of which comprises a mounting eye 6. Each mounting eye 6comprises a radial mounting aperture 7, and the base element 3 isarranged between the fork arms 5. The fork arms 5 overlap the baseelement 3 radially and receive the ends of the pivot axle 2 in theirmounting eyes 6. In this way, an axial fixing of the tension shoe 1relative to the base element 3 is obtained.

The base element 3 comprises a concave retention surface 8 and thetension shoe 1 comprises a convex retention surface 8. Both theretention surfaces 8, 9 are arranged coaxially with the pivot axle 2 andare situated opposite each other. From FIG. 1 it can be seen that, inthe shown position of pivot, the pivot axle 2 which is fixed on the baseelement 3 cannot be displaced out of the mounting eye 6 because theretention surfaces 8, 9 are pressed against each other in this directionof movement.

The tensioning device according to the invention represented in FIGS. 3and 4 differs from that of FIGS. 1 and 2 mainly by the followingfeatures: The pivot axle 2 is fixed on the tension shoe 1 and projectsfrom the tension shoe 1 on both sides.

The base element 3 comprises fork arms 10 between which the tension shoe1 is arranged. Each of the fork arms 10 comprises a mounting eye 11, andeach mounting eye 11 comprises a radial mounting aperture 12. Themounting eyes 11 receive the projecting ends of the pivot axle 2. It canbe seen from FIG. 3 that, in the shown position of pivot, a radialoutward displacement of the pivot axle 2 which is fixed on the tensionshoe 1 is impossible because the retention surfaces 8, 9 are pressedagainst each other in this direction of movement. From FIG. 4 it can beseen that the tension shoe 1 is secured against axial displacementrelative to the base element 3.

Finally, FIG. 5 again shows the tensioning device according to theinvention represented in FIG. 1, with the tension shoe 1 pivotedrelative to the base element 3 so that the retention surfaces 8, 9 aredisengaged from each other. In this position, the tension shoe 1 can bepushed without any problem onto the pivot axle 2. The representationalso shows that, in the region of the mounting aperture 7, the tensionshoe 1 comprises a constriction 13 whose clear width is smaller than thediameter of the pivot axle 2. During the insertion of the pivot axle 2into the mounting eye 6, the fork arms 5 are deformed elastically sothat the pivot axle 2 can pass the constriction 13 and come to besituated in the mounting eye 6.

LIST OF REFERENCE NUMERALS

1 Tension shoe

2 Pivot axle

3 Base element

4 Spring element

5 Fork arms

6 Mounting eye

7 Mounting aperture

8 Retention surface

9 Retention surface

10 Fork arms

11 Mounting eye

12 Mounting aperture

13 Constriction

What is claimed is:
 1. Tensioning device for a traction means,comprising a tensioning shoe (1), that tensions the traction means,andcomprising a further base element (3), on which the tensioning element(1) is mounted for pivoting on a pivot axle (2), a spring means (4)arranged between the elements (1, 3) urging the tensioning element (1)against the traction means, wherein one of the two elements (1, 3)comprises two horseshoe-shaped spaced-apart fork arms (5, 10) each ofwhich comprises a mounting eye (6, 11) having a radial mounting aperture(7, 12) for radially receiving the pivot axle (2), and the other of theelements (1, 3) comprises a radial projection (1, 3) which engagesbetween the forks (5, 10) and is overlapped by the forks (5, 10) on boththe elements (1, 3) for snap engagement without a separate fastener,there are corresponding arranged retention surfaces (8, 9) which extendcoaxially with the pivot axle (2) and which, within anoperation-dependent pivoting range of the tensioning device, aresituated opposite each other and face each other, a radial displacementof the pivot axle (2) out of the radial mounting aperture (7, 12) beingprevented by a contact of the retention surfaces (8, 9) with each other.2. Tensioning device according to claim 1 wherein the pivot axle (2) isfixed on the base element (3) and has ends projecting from both sides ofthe base element (3), each of which ends engages into one of the radialmounting apertures ((7) of one of the fork arms (5) which are fixed onthe tension shoe (1).
 3. Tensioning device according to claim 1 whereinthe pivot axle (2) is fixed on the tension shoe (1) and has endsprojecting from both sides of the tension shoe (1), each of which endsengages into one of the radial mounting apertures (12) of one of thefork arms (10) which are fixed on the base element (3).
 4. Tensioningdevice according to claim 1 wherein the retention surface (9) on tensionshoe (1) has a convex shape and the corresponding retention surface (8)on the base has a concave shape.
 5. Tensioning device according to claim1 wherein the radial mounting aperture (7) comprises a constriction (13)whose width is smaller than the diameter of the pivot axle (2). 6.Tensioning device according to claim 1 wherein the pivot axle (2) ismade in one piece with one of the two elements (1, 3).
 7. Tensioningdevice according to claim 1 wherein the pivot axle (2) is made in onepiece with one of the two elements (1, 3).